I stood with my toes at the edge of the wooden platform and stared down at the water-filled pit 10 feet below, feeling like an 8-year-old attempting the high dive for the first time. Even if other people were splashing around in it, the pool looked cold, dark and just a bit dangerous. But after climbing through a narrow hole in the Yucatan earth and down a steep ladder into the underground cave, I'd already made my decision.

I jumped, plunging feet-first into the depths. When I surfaced, I treaded aqua water, took in the mossy walls and stalagmites and wondered, "How the heck did I end up here?"

I'd come to the Yucatan peninsula with my wife and two friends looking for sun, seafood and mystical ruins.

Swimming in a cenote -- a sinkhole filled with fresh water dozens of feet below ground -- did not rank high on the list of things to do.

We'd heard that some cenotes can be touristy, packed with busloads of visitors and guys at the top vying to take you down for a fee. Then we met a couple of Minnesotans who live part of the year in Mérida, the Yucatan's largest city. They'd recently visited a chain of cenotes reached by horse-drawn carts that run on defunct rails. It was a mere hour's drive from Mérida, where we were staying.

Never mind that it was in the opposite direction of where we had planned to go. We were on a seven-day, 900-mile mostly unscripted road trip, which meant we were in charge of our itinerary -- and we changed it.

Valerie Coit, Star Tribune

To get to the cenotes from the village of Chunkanan, visitors ride in horse-drawn "trucks" along a narrow rail track.

Most literature we saw said the cenotes were in Cuzama, a town on a main road. They're actually south a few miles, in a village called Chunkanan. We had heard rumors of people being forced to pay unnecessary fees to get to the cenotes from Cuzama, so we decided to take a more circuitous, alternate route to Chunkanan.

In our rented Nissan Tsuru, an economical if not spartan sedan, we followed the highway from the city, then turned off on a backroad. In a matter of meters, the road narrowed, with jungle brush crawling right up to the road's edge.

Then came the twists and turns. And potholes.

We knew where the town was in relation to Mérida, but our maps failed us after we turned left off the highway. Conversation turned to, "Do you think we're on the right road? Are you sure it wasn't the left back there? Are we crazy?" My friend turned on his cellphone. We placed our faith in GPS.

A soft-drink delivery truck almost crushed us as it barreled around a blind corner. Occasionally, men with machetes in hand or rifles slung over their backs would emerge from the jungle with arms full of wood to bundle onto their bicycles. Villagers stared at us as we rolled slowly through pueblas, trying not to bottom out when we crossed over the many topes, severe speed bumps that punctuate the Yucatan roadways. On the outskirts of several villages, trash burned in open, unattended fields.

Finally, we saw a sign: "zona de cenotes." We'd arrived at Chunkanan.

A vinyl sign spelled out the price for the three-hour cenote tour: 250 pesos for a "truck," an open-air cart with wooden seats. That was less than $25 for four people.

A group of drivers and their "trukas" were lined up, like taxicabs at an airport, waiting for the next fare. The tours are the village's main economic engine, we learned, and the men of the village ran the service. Each driver gets one, maybe two, trips per day.

We motioned at the driver at the head of the line. He freed his horse from a nearby tree and took his seat at the front of the truck.

The horse, a gaunt roan named Canelo, started with a jerk as he pulled us through part of the village, the scent of citrus and woodfire in the air. We passed a few red buildings, scrub brush and spiky sisal plants until we found ourselves surrounded by shades of green in the jungle.

It was a bone-jarring, teeth-clacking, butt-numbing ride. The landscape looked so peaceful, yet the wheels of our truck clanked, jangled and scraped along the metal track once used to transport the sisal from field to factory. Chewing gum proved to be a good shock absorber.

There's only one track serving the three cenotes, named Chelantun, Chansinic'che and Bolonchoojol. When two trucks come upon each other, a frequent occurrence, both stop. One driver asks his passengers to get out, ties his horse to a tree and removes the truck so the other group can pass. Then he puts the truck back on the track, invites his passengers aboard and instructs the horse to move.

Underground pools revealed

Thousands of cenotes dot the Yucatan peninsula. According to Mayan legend, the water holes are sacred, a path to the underworld or afterlife. But they also served a far more practical purpose: providing fresh water on a peninsula with few rivers or lakes.

The Yucatan has a porous limestone base that acts as a filter as water makes its way below ground. Over time, the water erodes the rock and forms caverns. Sometimes the roofs of those caverns collapse, exposing the underground rivers and pools and creating a cenote.

Two of the cenotes we encountered had larger opening and stairways, but one was mostly covered except for a small hole and a vertical ladder that went down about 30 rungs. All smelled a bit musty, like a sidewalk after a spring rainfall.

There were platforms of various heights and sturdiness in each cavern. Gray and mossy stone walls ringed the water. Sunlight poked through holes to illuminate parts of the caves, but other areas remained dark.

Where the sunlight kissed the water, it shone the most vivid, electrified blue I had ever seen. Away from the light's reach, the aquamarine shade turned to India ink.

The water was clear and refreshing, warmer than it looked. Fish darted in the shallows. Water plopped down in drips from above.

Viewed with the help of a snorkel and mask, the scene below water is surreal. Craggy stalagmites create intricate designs in the shallows. In some spots there seems no end to the watery depth.

After exploring the pools, we climbed carefully out of the caves and back above ground. Temps in the 80s and warm sun quickly dried us out as we returned along the bumpy track.

At the village, we thanked our driver and strolled to the tiny convenience store. There we bought water, chili-lime peanuts and Cokes and hoped for more unplanned outings as enjoyable as this one.

"Women of the flats stood guard over their thresholds while police attempted to eject them for failure to pay rent on the grounds on which the dwellings stand. A near-riot was halted when a second court order was served on police, ordering a stay of the ejections."